Abrasive articles are used in a variety of fields for abrading material from a surface of a workpiece. For example, a circular abrasive disc may be releasably mounted on a back-up pad for rotative movement by a random orbital sander. When the disc is rotated, and the exposed abrasive surface of the disc is urged against the workpiece surface, material may be removed from the workpiece. This operation may be desirable for surface refinement purposes, or for the removal of excess material from the workpiece.
Abrasive discs and sheets often have some type of integral attachment system, to enable the disc or sheet to be releasably attached to a back-up pad. Three such abrasive discs that are relevant to the present invention—discs with pressure sensitive adhesive, textile materials, and stalks, respectively—are described seriatim below.
One type of abrasive disc includes an integral layer of pressure sensitive adhesive (“PSA”) on the back surface of the disc. The PSA adheres the disc to the back-up pad, and is sufficiently aggressive to prevent displacement of the abrasive article with respect to the back-up pad during use. Furthermore, the PSA permits the abrasive article to be peeled away from the back-up pad relatively easily, such that a new abrasive disc may be applied to the back-up pad with a minimum of time and effort.
Although they have certain benefits, PSA abrasive discs also have some limitations. For example, the PSA can be too aggressive in its adhesion to the back-up pad, such that the operator may be unable to remove all of the abrasive article from the back-up pad. If pieces of the disc backing or areas of PSA, or both, are left on the back-up pad, the resultant buildup can cause high spots on the back-up pad and present an uneven and unbalanced operating surface for receipt of a new abrasive disc. This unevenness may leave undesirable streaks or marks on the surface being abraded. Another potential deficiency of the PSA abrasive disc is that the disc is intended for only a single use, because the PSA layer becomes easily contaminated with dust and debris when it has been detached from the back-up pad. When the PSA layer has been contaminated, reattachment to the back-up pad is difficult or impossible, and a new disc must be provided. This single use characteristic thus can be wasteful, because an abrasive disc may have to be discarded before the abrasive surface has worn out.
Another type of abrasive disc, referred to herein as the “textile” disc, includes a textile loop material on the rear surface of the abrasive article. The textile material can be, for example, woven or non-woven web, brushed nylon, brushed polyester, knitted fabrics, and stitch-bonded fabrics. Textile discs are described in U.S. Pat. No. 4,437,269 (Shaw) and U.S. Pat. No. 4,609,581 (Ott), and an example of a textile abrasive disc is available from the Minnesota Mining and Manufacturing Company of St. Paul, Minn. under the designation Hookit™ discs. Textile discs are typically used in conjunction with a back-up pad having a plurality of engaging members that are bonded to the attachment surface of the back-up pad. The engaging members on the back-up pad are designed to engage the textile material of the textile disc, to secure the abrasive disc to the back-up pad.
Textile abrasive discs overcome some of the disadvantages associated with PSA discs. For example, textile abrasive discs may be removed from and reattached to the back-up pad several times, even if the textile material is exposed to dust or dirt. Thus, textile discs may be used several times before they must be discarded. Also, the textile material does not leave any adhesive residue on the back-up pad.
Textile abrasive discs, however, also exhibit some disadvantages. For example, textile discs can shift relative to the back-up pad during use, especially when the textile is a low weight material. Also, if the textile material is damaged during disengagement from the back-up pad, the disc may be limited to a single use. Furthermore, fibers from the textile material tend to come loose from the abrasive disc, which can clog the engaging members on the back-up pad. The loose fibers may also become airborne, which is undesirable in some environments where, for example, surfaces prepared for painting or freshly painted surfaces are present. Also, when textile abrasive discs are stacked (for handling during packaging, for example) the abrasive grains of one disc can snag the textile material on an adjacent disc, rendering the abrasive discs difficult to separate. Textile abrasive discs are also typically more expensive to manufacture than PSA discs.
U.S. Pat. No. 4,437,269 (Shaw) relates primarily to textile discs of the type described above, but also briefly discusses a final type of disc referred to herein as the “stalk” disc. Specifically, the '269 patent discloses a back-up pad and a disc, wherein one of the two components has a textile material on one face, and “the other of the pad and the back of the disc ha[s] a layer thereon from which extend loop-engaging or curl-engaging members in the form of mono-filament stalks having un-hooked ends.” See column 2, lines 55 through 58 of the '269 patent. The stalks project from a backing, and slidingly intermesh with, but do not hook, a loop-like textile material on an opposed surface to attach the two surfaces together.
The abrasive disc of the '269 patent, with one side including stalks having unhooked ends, also may not perform acceptably under some circumstances. For example, it may be desirable for an abrasive disc to exhibit a certain minimum level of peel adhesion force, which may be difficult to attain using a structure such as that shown in the '269 patent.
In view of the disadvantages associated with the various abrasive discs of the prior art, it is desirable to provide an abrasive disc that is relatively inexpensive, reusable, easily and securely attached to a back-up pad, and easily removed from the back-up pad for replacement.